Proposed is a railcar bogie from which side sills are omitted in such a manner that: each of plate springs extends between front and rear axle boxes; and longitudinal direction middle portions of the plate springs support a cross beam (see PTL 1). To be specific, in this bogie, the plate spring achieves the function of a suspension and the function of a conventional side sill. To reduce the weight of the bogie, the plate springs are formed by using fiber-reinforced resin.
While the bogie is traveling, loads are repeatedly applied to the plate springs. Therefore, regarding the plate springs that have been used for a long period of time, attention to strength deterioration by fatigue is necessary. Here, realizing simple monitoring of the state of the plate spring itself is useful for an improvement of maintenance efficiency of the bogie. For example, PTL 2 discloses a technique in which: a plurality of electrodes are arranged at predetermined intervals on one of surfaces of a composite material made of CFRP; and abnormality of the composite material is detected from a change in electrical resistance measured based on current flowing between the electrodes.